This invention relates generally to electronic test instruments and particularly to multimeters of the type used for measuring parameters such as AC voltage and current, DC voltage and current and resistance. Such instruments with a digital display are known as digital multimeters or DMM""s. Some of these instruments are equipped with a clamp for surrounding a cable or bus for the purpose of measuring current without tapping into the cable. The present invention adds functions to an electronic test instrument beyond what has been provided in the past. A recurring safety issue for electricians is determining whether it is safe to work on a particular line or cable, i.e., whether the line is live or dead. The present invention provides the capability of making that determination quickly through either tactile or visual indicators.
An electronic test instrument is provided with a shaker motor that provides a tactile indication of the presence of a voltage. The shaker motor vibrates at a speed that is proportional to the voltage level, thereby providing a general sense to the user of the voltage level""s magnitude. The instrument may further include a clean power circuit that detects the presence of excessive harmonic distortion and noise on an AC signal. Finally, the test instrument may have a clamp with a built-in non-contact voltage sensor.